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Date:	Wed, 16 Jul 2014 09:13:07 +0200
From:	Eric Dumazet <>
To:	David Held <>
Subject: Re: [PATCH net-next v3 2/2] udp: Use hash2 for long hash1 chains in

On Tue, 2014-07-15 at 23:28 -0400, David Held wrote:
> Many multicast sources can have the same port which can result in a very
> large list when hashing by port only. Hash by address and port instead
> if this is the case. This makes multicast more similar to unicast.
> On a 24-core machine receiving from 500 multicast sockets on the same
> port, before this patch 80% of system CPU was used up by spin locking
> and only ~25% of packets were successfully delivered.
> With this patch, all packets are delivered and kernel overhead is ~8%
> system CPU on spinlocks.
> Signed-off-by: David Held <>
> ---

Signed-off-by: Eric Dumazet <>

Thanks David.

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